Percussionaire — Bird Respirator History Wiki — Ventilator
John, Thanks for the presentation. https://www.johndcook.com/blog/2010/07/13/lincoln-index/ How many errors are left to find?
Here is a beautiful website by Grant Sanderson. 3blue1brown So many exciting insightful mathematics presentations. The craft and artistry are as impressive as the mathematical concepts. Take a look — even if you think you know the material — you will see a few new gems (I bet).
Take a photo of a handwritten math problem and get the answer from your smartphone https://photomath.net/en/